A passenger car with a roof diffusor in the tail region is known from publication DE 943 746. This roof diffusor serves for lowering the aerodynamic drag of automobiles and similar vehicles. While driving forward, a certain quantity of air is displaced by the automobile on its front side and moves rearward relative to the automobile with a speed that is higher than the driving speed. Consequently, a negative pressure exists around the roof and the sides of the automobile. The air can disperse in the space situated behind the automobile. The relative air speed decreases and the static pressure increases. The air friction laws for a diffusor apply to this process.
For this purpose, a diffusor is arranged on the tail end of the car in the above-cited publication. This diffusor features a rearwardly open chamber that is bounded by sidewalls and the closed forward-facing wall section of which is rounded. Referred to the entire vehicle, this diffusor has relatively small dimensions. The chamber forms a curved chamber ceiling. The height of the chamber opening is smaller than the greatest chamber height. Due to the ejector effect, the air flowing past the chamber generates a partial vacuum therein such that the air is sucked in behind the chamber downstream of the automobile roof and exerts an increased pressure upon the rear part of the automobile as its air speed decreases in order to thusly lower the aerodynamic drag for the automobile.
A motor vehicle with an air deflector device is known from publication DE 10 2004 047 882 A1. An ascending underbody is provided in the tail region of the vehicle in order to form a diffusor. An air deflector device in the form of a plane plate is provided transverse to the flow direction in a second half of the diffusor. In this case, the diffusor reduces the aerodynamic drag of the vehicle in cooperation with the plate and at the same time minimally increases the aerodynamic lift in the tail region.
It is the objective of the application to develop a fastback for a passenger car that makes it possible to further lower the aerodynamic drag of a vehicle. In addition, other objectives, desirable features and characteristics will become apparent from the subsequent detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.